The present invention relates to a pulley for transmitting torque from an external drive source to a rotary shaft thereby driving a compression mechanism. The present invention also pertains to a compressor having such a pulley.
Typically, a damper mechanism is employed for reducing torque fluctuations in a rotary shaft of a rotation apparatus, thereby preventing resonance. Such a damper mechanism is coupled, for example, to the output shaft of a drive source such as an engine or to the input shaft of a driven rotational apparatus such as a compressor. When used in a compressor, a damper mechanism is generally coupled to a rotary shaft of the compressor, which is coupled to an engine through rotors such as a hub and a pulley. Also, a certain type of damper mechanism is located in a hub or a pulley.
For example, Japanese Laid-Open Patent Publication No. 9-317628 discloses a dynamic damper used in a compressor. The dynamic damper includes an elastic member and a mass body. The elastic member is attached to one end of the rotary shaft of the compressor. The mass body is coupled to the rotary shaft through the elastic member. When the rotary shaft is torsionally vibrated due to compression of gas by the pistons, the mass body is resonated to consume the kinetic energy, which suppresses the peaks of torque fluctuations caused by the torsional vibration. Accordingly, resonance generated between the compressor and other devices (external rotational apparatus) is reduced.
Pendulum type damper mechanisms, which are typically used for engines, are also known in the art. A pendulum type damper mechanism includes a rotor, which is fixed to the crankshaft of the engine. A pendulum is attached to the rotor. Swinging of the pendulum suppresses the peaks of torque fluctuations due to torsional vibrations of the crankshaft. The pendulum swings about an axis that is spaced from the rotation axis of the rotor by a predetermined distance and is parallel to the rotation axis of the rotor.
In the former structure, the mass body, which is accommodated in the housing, is relatively large and heavy. This increases the weight and the size of the compressor. Also, the mass body is attached to the rotary shaft through the elastic member, which is influenced by temperature changes. Therefore, it is difficult to match the characteristic frequency of the dynamic damper with the frequency of the peaks of the torsional vibrations of the rotary shaft (the frequency of the peaks of the torque fluctuations).
In the latter structure, the pendulum is connected to the crankshaft through the rotor, which increases the weight and the size of the rotor.
In the dynamic damper disclosed in Japanese Laid-Open Patent Publication No. 2000-274489, each of roller mass bodies reciprocates along a cylindrical path.
The mass body is accommodated in a guiding portion (accommodation chamber) formed in the rotor. Part of the inner surface of the guide portion is formed as a part of the inner surface of a cylinder. The center of curvature of the cylinder is an axis that is spaced from the rotation axis of the rotor by a predetermined distance and is parallel to the rotation axis of the rotor. When the rotor rotates, centrifugal force presses the mass body against the cylinder inner surface. In this state, torque fluctuations of the rotary shaft are received by the rotor and swing the mass body along the cylinder inner surface.
Sliding movement of the mass body on the cylinder inner surface wears the mass body and the cylinder inner surface, or the rotor. This will change the shape of the mass and the shape of the cylindrical inner surface. As a result, the settings for effectively preventing resonance are changed, which degrades the resonance prevention performance. Further, the wear shortens the life of the rotor, or the rotation apparatus.
Accordingly, it is an objective of the present invention to provide a compressor having a compact and light pulley that is easily adjusted to reduce resonance. Another objective of the present invention is to provide a compressor that prevents its resonance reduction performance from deteriorating and its life from being shortened.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, a compressor is provided. The compressor has a pulley for transmitting torque from an external drive source to a rotary shaft to drive a compression mechanism. The pulley has a pulley body. The compressor comprises a mass body located in a range that is radially inward of the outer circumference of the pulley. The mass body swings about an axis that is spaced from the rotation axis of the pulley body by a predetermined distance and is substantially parallel to the rotation axis of the pulley body.
The present invention also provides a pulley for a compressor. The pulley comprises a pulley body and a mass body. The mass body is located in a range that is radially inward of the outer circumference of the pulley. The mass body swings about an axis that is spaced from the rotation axis of the pulley body by a predetermined distance and is substantially parallel to the rotation axis of the pulley body.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.